Question 1

What is the difference between a lab experiment and a field experiment?

Accepted Answer

A lab experiment takes place in a controlled environment where the researcher manipulates the IV and controls extraneous variables, offering high internal validity. A field experiment occurs in a natural setting, increasing mundane realism and reducing demand characteristics, but with less control over confounding variables. For example, Loftus and Palmer's lab study on eyewitness testimony vs. a field study on bystander intervention.

Question 2

How do I choose which inferential test to use?

Accepted Answer

You need to consider three things: the experimental design (independent groups, repeated measures, or matched pairs), the level of measurement (nominal, ordinal, interval), and whether you're looking for a difference or a correlation. For independent groups with ordinal data, use Mann-Whitney U; for repeated measures with ordinal data, use Wilcoxon signed ranks; for correlations with ordinal data, use Spearman's rho. Always check the conditions in your formula sheet.

Question 3

What is a type 1 error and how can it be avoided?

Accepted Answer

A Type 1 error occurs when you reject the null hypothesis when it is actually true—essentially a false positive. This is more likely if you set a lenient significance level (e.g., p ≤ 0.10). To avoid it, use a stricter significance level like p ≤ 0.05 or p ≤ 0.01, and ensure your sample size is adequate. In psychology, we accept a 5% chance of Type 1 error as standard.

Question 4

Why is random sampling often not used in psychology?

Accepted Answer

Random sampling is ideal for generalisability, but it's often impractical because you need a complete list of the target population (sampling frame), which is hard to obtain. It's also time-consuming and expensive. Psychologists often use opportunity or volunteer sampling instead, which are quicker but introduce bias. For example, a university study using volunteer sampling may only attract certain personality types.

Question 5

How do I evaluate a study's validity?

Accepted Answer

Validity refers to whether the study measures what it claims to. Consider internal validity (did the IV cause the DV?) and external validity (can findings be generalised?). Look for demand characteristics, experimenter bias, and confounding variables. For example, in Milgram's study, high internal validity due to controlled conditions, but low ecological validity because the lab setting was artificial.

Question 6

What is the difference between a null hypothesis and an alternative hypothesis?

Accepted Answer

The null hypothesis (H0) states there is no effect or relationship, e.g., 'There is no difference in memory recall between music and no-music conditions.' The alternative hypothesis (H1) predicts an effect, e.g., 'Participants in the no-music condition will recall more words than those in the music condition.' In inferential testing, we aim to reject H0 if the observed result is significant.

Research methods and techniques

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